Electroplating of chromiummolybdenum alloys



July 25, 1950 Q M 2,516,227

ELECTROPLATING 0F CHROMIUM-MOLYBDENUM ALLOYS Filed March 10, 1945 IN VENTO R Gf/U/f c/mva M/l WWW/'7.

ATTORNEY Patented July 25, 1950 ELECTROPLATIN G OF MOLYBDENUM ALLOYS.Chuk Ching Man-Orange; N. .I.,,a ssignr;to'jWest-.inghouse.Electricflorporatim, East Pittsburgh, Pa., a corporation ofPennsylvania,

Application March 10, 1945, Serial No. 582,004

2 Claims. ,(Cl. 204-43) invention relates --to electroplating and, moreparticularly, to such a process applied to alloys of chromiumand-molybdenum.

The principalobject of myinvention,-generally chromium and molybdenum inaccordance with my invention isfeasible :because of the-unusualproperties of the alloying metals. These properties supplementoneanother so. that the alloy considered, is to deposit alloys ei'chromium and isresistant to more chemicals thaneitherof the molybdenumfrom aqueous solutions in dense constituents thereof. For example, whilechroclosely-adherent form.- mlum is solublein hydrochloric and .cold.dilute Another object. of myinvention is to plate hydrofluoric acids,molybdenum is insoluble, so alloys of chromium and molybdenum from thatan alloy of the two is resistant .to these aqueous'solutions, suchalloys to contain from acids. .0n the other hand, while molybdenum is-1%' to 30% of molybdenum; soluble in nitric acid, chromium isinsoluble/so A further object of my inven'tion is to-coat base that thealloy isresistant to that .acid. While metal, suchas .copperand iron,with a dense, chromium is solubleein dilute sulphuric acid,closely-adherent plating of an alloy such as molbdenum is only slightlysolubleso that the chromium-molyb'denumzwhichis highly resistant alloyis resistant'tothat acid. tov oxidation and the corrosive .action ofReferring nowtothedrawing, :there is shown chemicals. a-container l inwhich is Iasolution 210i molybdic Other objects and advantages of theinvenacid in chromic acid. The proportion is desirtion will becomeapparent as the description ably about three times the weight of chromicproceeds. oxide (0103) that there is of molybdenum tri- Referring to thedrawing, the single figure oxide (M003). The solution is acidulated withshows in vertical section a container holding a sulphuric acid(desirably about 1% of the weight plating bath, in which are immersed apair of coof the chromic oxide) to improve its conductivity. operatingelectrodes. The weight of the water inmaking the bath is Chromium may beplated from solution, but is desirably from 3 to 10 times that of thechromic ordinarily formed by the reduction of chromium oxide. The anode3 may be formed of some maoxide by aluminum. Molybdenum in themetalterial such as platinum which does not dissolve lic form isproducible by reduction of the oxide in the bath during the platingoperation, but is by carbon or hydrogen. However, it cannot be desirablyformed of molybdenum or chromiumdeposited by itself from aqueoussolution as a molybdenum alloy which passes into solution plating. Bothchromium and molybdenum, during the operation and thereby avoids adeplehowever, are in group VI of the periodic table tion of themolybdenum content of the bath. of the elements and there, therefore,appeared The cathode 4 may be of any shape desired and to be a po y oco-d position from an formed of copper, iron, molybdenum or anyconaqueous solution which contained both chromium ductive material whichis desired to plate for any and molybdenum ions. purpose, such forexample to protect from oxida- FOr the P p O determining Whether iihiStion or corrosion by the alloy plating. The platwas p s l I diss lvedmolybdenum trio id in ing time depends on the desired thickness of the asolution of chromic acid and was able to dell coating, The proportion ofohromio oxide posit alloys of chromium and molybdenum on a to ulphuricacid is tri tly governed by t fol. cathode immersed in said solution. Ifound lowing m; that such plating was in dense closely-adherent form,thereby well serving to protect the metal Wt. of CI'Oc 100 or 50 onwhich deposited from oxidation and corrosive we of H2504 or tequivalent, action. 4

The protection of readily oxidizable metals 5 The fol w g table gives aSummary Of s e such as iron, copper, etc., by plating the same of the Wr W c I have performed in plating with a densely-adherent coating of analloy of metal with chromium-molybdenum alloys- Composition of the bathAnode Cathode 535$; Time Temp. g gifi i g g oro M003 H2804 H 0 GramsGrams Grams Grams Hours C'. Inches Per Cent 15 0. 45 300 15 5 40 0.0044.5 30 1o 0. 30 200 15 5 40 0.003 22.4 00 20 0. 00 200 25 5 40 0.005 207 0. 20 200 15 5 room 0.004

1 Not tested.

From the foregoing disclosure, it will be seen that I have devised amethod of plating alloys of chromium and molybdenum from aqueoussolutions, said alloys being deposited as dense coherent plate on thecathode of the plating bath. The plating is useful for protecting theplated article from oxidation, chemical corrosion, as well as giving itan attractive finish.

Although a preferred embodiment of my invention has been disclosed, itwill be understood that modifications may be made within the spirit and.scope of the appended claims.

I claim: 1

1. The method of electroplating comprising dissolving chromic oxide infrom 6 to 7- times its weight of water, dissolving molybdenum trioxideequivalent to about /3 the weight of chromic oxide in said solution,adding sulphuric acid equivalent to about 1% of the weight of thechromic oxide, heating to a temperature up to 40 C., and passingelectric current therethrough,

using a base metal cathode and an anode of molybdenum, and continuingthe passage of said current for about five hours to form a deposit onthe cathode of a molybdenum-chromium alloy containing from 1% to 30% ofclosely-adherent form.

2. The method of electroplating comprising dissolving chromic oxide infrom 6 to 7 times its weight of water, dissolving molybdenum trioxidemolybdenum in equivalent to about the weight of chromic oxide in saidsolution, adding sulphuric acid equivalent to about 1% of the weight ofthe chromic oxide,

heating to a temperature up to C., and passing electric currenttherethrough, using a base metal cathode and an anode of molybdenum, toform a deposit on the cathode of a molybdenumchromium alloy containingfrom 1% to 30% of molybdenum in closely-adherent form.

CHUK CHING MA.

REFERENCES CITED The following references are of record in the file ofthis patent:

V UNITED STATES PATENTS Number Name Date 1,365,499 Kelley Jan. 11, 19211,581,188 Fink Apr. 20, 1926 1,717,468 Schulte June 18, 1929 1,782 .092Gray et a1 Nov. 18, 1930 1,795,459 Westbrook Mar. 10, 1931 1,885,700Fink Nov. 1, 1932 1,993,020 Scott Mar. 5, 1935 2,332,416 Waltenberg Oct.19, 19%3 2,392,821 Kreag Jan. 15, 1946 FOREIGN PATENTS Number CountryDate 240,490 Great Britain Sept. 16, 1926 286,457 Great'iBritain Mar. 8,1928 OTHER. REFERENCES J. Am. Chem. Soc., 54, 1932 (3775-6) Trans.Electro. Chem. Soc, vol. .70 (1936) pp. 423-429.

1. THE METHOD OF ELECTROPLATING COMPRISING DISSOLVING CHROMIC OXIDE INFROM 6 TO 7 TIMES ITS WEIGHT OF WATER, DISSOLVING MOLYBDENUM TRIOXIDEEQUIVALENT TO ABOUT 1/3 THE WEIGHT OF CHROMIC OXIDE IN SAID SOLUTION,ADDING SULPHURIC ACID EQUIVALENT TO ABOUT 1% OF THE WEIGHT OF THECHROMIC OXIDE, HEATING TO A TEMPERATURE UP TO 40*C., AND PASSINGELECTRIC CURRENT THERETHROUGH, USING A BASE METAL CATHODE AND AN ANODEOF MOLYBDENUM, AND CONTINUING THE PASSAGE OF SAID CURRENT FOR ABOUT FIVEHOURS TO FORM A DEPOSIT ON THE CATHODE OF A MOLYBDENUM-CHROMIUM ALLOYCONTAINING FROM 1% TO 30% OF MOLYBDENUM IN CLOSELY-ADHERENT FORM.